/Engine/Source/Runtime/CoreUObject/Public/UObject/PackageTrailer.h
Serializes the trailer from the given archive assuming that the seek position of the archive is already at the correct position for the trailer.
True if a valid trailer was found and was able to be loaded, otherwise false. If the trailer was found but failed to load then the archive will be set to the error state.
bool TryLoad ( [FArchive](API\Runtime\Core\Serialization\FArchive) & Ar )